The fact that vehicle storage batteries are more effective for starting a vehicle engine when kept warm is well known. Numerous schemes for heating batteries have been proposed. The applicants have discovered that by inducing fluid motion currents in the electrolyte with a trickle charge, the battery can be easily and efficiently warmed in conditions of extreme cold.
Systems for simultaneously heating and charging a vehicle battery have been proposed. See, for example, Bachmann U.S. Pat. No. 3,110,633 which discloses heating and charging a vehicle battery with energy supplied by the generator or alternator when the vehicle engine is running. Carlson U.S. Pat. No. 3,469,072 teaches heating and charging simultaneously when the engine is running but only heating when the engine is not running. Edlund et al. U.S. Pat. No. 3,870,855 teaches a timer-controlled circuit for heating the engine, the cab and charging the battery. No control of the charging current or the heater temperature is provided. Miyahara U.S. Pat. No. 4,081,737 teaches simultaneously charging and heating a battery but with no individual control of the heating and charging circuits.